Tuesday, June 14, 2016

Tonight's Sky for June 14: The Earliest Sunrises

While
the solstice (and shortest nights) will not occur for about another
week, the earliest sunrises occur now. Why is this? Short answer:
celestial mechanics. As for why the Sun doesn't have its extreme
rise/set dates on the day of the solstice, it all has to do with
solar noon, the point in time wherein the Sun reaches its highest
point in the sky, which is the basis for the timing of the solstice.
Problem: the Sun doesn't always reach its highest point in the sky as
seen from Earth at noon. In contrast, the Sun is at its peak
elevation about a week before the solstice in summer, which means
that, solar noon being about 8 minutes before Earth noon, that also
means that the sunrise occurs about 8 minutes earlier, too.